How can people be so happy for so long, only to then have the marriage turn sour in what are supposed to be their "golden years" together? Some relationships have been in decline for decades and finally lose all their juice. It's more like a balloon that has been seeping air for a long time. Another possibility is that a couple's issues intensify.Most problems are manageable, but then something sends them into hyperdrive.

However, one of the most common reasons people end up in long distance relationships is because of college.

En español | By now, it's an old story: one-half of a high-profile and long-married couple — usually the man, truth be told — admits to having an affair.

Sometimes, the couple's marriage can withstand the infidelity; other times, the breach of trust is too deep, and a split or divorce ensues.

Not only are they a pain to maintain, but they also tend to be destined for failure in the long run. This number was more or less the same with an estimation of about 14 million in 2017.

Furthermore, of that 14 million, almost four to four and a half million of these couples are in a non-marital relationship.